1. Field of the Invention
This invention relates to the structure of a camera to prevent electromagnetic wave noises from affecting a photo-electro transducer which is disposed within the camera for receiving light.
2. Description of the Prior Art
Generally, a camera is provided with a photo-electro transducer for measuring the brightness of an object to be photographed. Especially in recent years, highly sensitive elements such as a silicon photo cell (SPC), a silicon photo diode (SPD), etc. have come to be used as photo-electro transducer. However, they are highly vulnerable to external electromagnetic wave noises. In the past, the body and other exterior parts of a camera were made of a metal material. Such a metal material served as a shield to protect the photo-electro transducer from the external electromagnetic wave noises. Therefore, the use of a photo-electro transducer in the past presented no problem in respect to the adverse effect of the external electromagnetic wave noises on the photo-electro transducer.
Meanwhile, the recent rapid advancement of plastic materials and the processing technique relative thereto has resulted in the use of them for camera bodies, exterior parts of cameras and other structural parts to a great extent for a reduction in the camera weight and cost. However, plastic materials for cameras are mostly an ABS resin, poly carbonate, etc. which have an electrical insulating property. Therefore, they are incapable of serving as a shield against external electromagnetic noises. The use of plastic materials thus greatly affects the accuracy of light measurement with external electromagnetic wave noises coming to the photo-electro transducer. However, conventional arrangement to have upper lid or the like of a camera which is made of an insulating plastic material plated with nickel, copper, chromium, etc. has somehow secured the shielding effect required.
Recent cost reduction efforts have brought forth a tendency to omit such plating. This tendency now presents a serious problem in respect to the adverse effects of external electromagnetic wave noises on the photo-electro transducer.
It is an object of the present invention to provide a camera incorporating a photo-electro transducer in which the members of the camera encompassing the photo-electro transducer are electrically conductive; and particularly, a support frame which accommodates and carries the transducer is made of a conductive plastic material formed with carbon black mixed therein to prevent external electromagnetic wave noises from affecting the photo-electro transducer, so that the camera has an accurately operating photo-electro transducer firmly arranged therein.
It is a second object of the invention to provide a camera having a photo-electro transducer in which the support frame is unified with a penta-prism box in such a way that variations in the mounting position of the photo-electro transducer are obviated; the support frame can be grounded without difficulty; and, in the manufacture of the camera, the assembly work can be simplified.
These and further objects and features of the invention will become apparent from the following detailed description of a preferred embodiment thereof taken in conjuction with the accompanying drawings.